The Metrological Qualification of Commercial VOC Multisensor Systems: A Mandatory Step Prior to Indoor Air Quality Monitoring

The use of multisensor array systems has become commonplace in indoor air quality or individual exposure applications. Nevertheless, there is a lack of reliable data, as qualification protocols are sparsely applied by end users to multisensor commercial systems prior to field or lab implementation. This is especially the case with regard to volatile organic compound (VOC) monitoring, although they are ubiquitous species of indoor environment. The aim of the present work is to propose an all-encompassing qualification protocol, suitable for a wide range of multisensor systems, able to assess the metrological performance regarding indoor VOCs. Furthermore, it provides data on metrological performance for 45 replicas of five types of sensors, four metal oxides, and one electrochemical, embedded in a single system, under controlled conditions. Multisensor systems were exposed to six single VOCs, with their mixture representative of indoor pollution (formaldehyde, acetaldehyde, acetone, ethanol, and limonene) in a 1:1 scale experimental room. Metrological performances were retrieved from the correlation curves established by comparison with the responses of a reference analyzer. The results show that the electrochemical sensor, supposedly dedicated to total VOCs, is acetone-blind and underestimates the effective quantity of total VOCs (TVOCs) by a factor of 3. Metal oxide sensors, chosen for their reliability in establishing pollution source fingerprints, indicate effectively differentiated sensitivities by type of VOC, but without homogeneity by chemical family. A preprocessing of the data is required to overcome their nonlinear responses depending on the concentration range. These results provide crucial insights for the interpretation of field campaign data retrieved from multisensor arrays.